The present invention relates to a gyro platform assembly that can detect angular drift of sensing axes that are along three orthogonal axes.
Carrouseling has been used in the past to detect angular drifts of sensing axes that are perpendicular to a carrousel axis. Carrouseling of a platform has not been effective in detecting angular drift of a sensing axis of the rate gyro, wherein the sensing axis is parallel to the carrousel axis of the platform.
The disclosed assembly can be used to determine drift rates in three different mutually orthogonal vehicle motion sensing axes. The assembly has a platform that carrousels around a carrousel axis. A gyro on the first platform has a vehicle roll sensing axis that is parallel to the carrousel axis of the first platform and perpendicular to the carrousel axis of the second platform. The gyro on the first platform also has a vehicle yaw sensing axis that is perpendicular to the carrousel axis of the first platform and perpendicular to the carrousel axis of the second platform.
The assembly also has a second platform that is within the first platform. The second platform carrousels around a carrousel axis that is perpendicular to the carrousel axis of the first platform. A gyro on the second platform has a vehicle pitch sensing axis that is perpendicular to the carrousel axis of the first platform and parallel to the carrousel axis of the second platform. The second gyro further has a vehicle roll sensing axis that is parallel to the carrousel axis of the first platform and perpendicular to the carrousel axis of the second platform.
By carrouseling the first platform, one can determine the drift rate of the yaw sensing axis of the gyro on the first platform. One can also determine the drift rate of the pitch Sensing axis of a gyro on the second platform by carrouseling the first platform. The first platform would be returned to its original position. The drift rate of the roll sensing axis of the rate gyro on the second platform can then be determined by carrouseling the second platform. Then the drift rate of the roll sensing axis of the rate gyro on the first platform can be determined from the known drift rate of the roll sensing axis of the rate gyro on the second platform. Thus drift in three orthogonal directions, that is along the above named yaw, pitch and roll sensing axes, could be determined by use of the above described assembly.
The gyro platform assembly of the present invention can detect a angular drift rate of a sensing axis of a rate gyro on a first platform, even though the-sensing axis of the rate gyro on a first platform is parallel to a carrousel axis of the first platform. First, a sensing axis of a rate gyro on the second platform is made parallel to the sensing axis of the gyro on the first platform. Then, by carrouseling the second platform, the drift rate of the sensing axis of the rate gyro on the second platform is determined. The drift rate of the sensing axis of the rate gyro on the first platform, that is parallel to the first carrousel axis, can then be determined based on the determined drift rate of the sensing axis of the rate gyro on the second platform.
More specifically, the output of the sensing axis of the rate gyro on the first platform, that is parallel to the carrousel axis of the first platform, is measured. This output is due to the angular rotation rate of the first platform around this sensing axis. The output of the sensing axis of the rate gyro on the second platform, that is parallel to the first carrousel axis, is also measured. This output is due to the angular rotation rate of the first and second platforms around this latter sensing axis. The second platform is then carrouseled 180 degrees. The output of the sensing axis of the rate gyro on the second platform is again measured. The outputs of the parallel sensing axes of the rate gyros on the first and second platforms, plus the output of the sensing axis of the rate gyro on the second platform after the second platform has been carrouseled 180 degrees, are used in an algorithm to determine angular drift rate of the sensing axis of the rate gyro on the first platform. The calculated angular drift rate can be used in a computer to determine the true angular rotation of the assembly around the sensing axis of the rate gyro on the first platform.